1. Field of the Invention
The present invention generally relates to a cylinder block of an internal combustion engine, and more particularly, to a reinforced structure of the cylinder block.
2. Description of the Prior Art
U.S. Pat. No. 4,831,978 discloses a reinforced structure of a cylinder block of an internal combustion engine. A plurality of bearings, in which a crank shaft is journaled, are received in the cylinder block and have respective caps rigidly secured thereto. The crank shaft extends through an opening formed in a rear cover of the cylinder block. A reinforcing member is fastened to a lower surface of a skirt portion of the cylinder block by means of bolts.
In this kind of cylinder block, the reinforcing member is also fastened to the rear cover by means of bolts so that oil contained in the cylinder block may not leak outside through the joint between the rear cover and the reinforcing member. Notwithstanding this fact, oil leakage occasionally occurs for such a structure.
More specifically, the cylinder block of the above-described type is provided with an oil seal interposed between the inner periphery of the opening of the rear cover and the outer periphery of the rear end of the crank shaft for preventing oil leakage. Because of this, the bolts for fastening the reinforcing member to the rear cover cannot be provided near the central portion of the lower surface of the rear cover due to the location of the outer diameter of the oil seal. Particularly, the rear end of the crank shaft is made larger in diameter because a transmission is connected thereto, thus inevitably causing the oil seal to be large in diameter. As a result, the problem arises that the pitch of the bolts for fastening the reinforcing member to the rear cover becomes long.
Accordingly, these fastening bolts cannot ensure sufficient surface pressure, thus occasionally causing oil leakage through the joint between the rear cover and the reinforcing member secured thereto.